1. Field of the Invention
The present invention relates to a front fork of a motor cycle or the like.
2. Description of the Related Art
In conventional forks, as a front fork of a motor cycle or the like, there is a structure in which a vehicle body side tube is slidably inserted into an axle side tube. A hollow pipe is provided in a standing manner in a bottom portion of the axle side tube. An oil chamber provided in an outer side of the hollow pipe is divided into upper and lower sides by a piston provided in a leading end portion of the vehicle body side tube. An oil reservoir chamber communicating with the oil chamber is provided in an inner side of the hollow pipe. A partition wall member for dividing the oil reservoir chamber into upper and lower sides is provided in an upper portion of the hollow pipe. A flow path communicating the upper and lower oil reservoir chambers is formed in the partition wall member. A compression side damping valve is provided in the flow path, and a gas chamber in an upper portion of the oil reservoir chamber is provided in an inner portion of the vehicle body side tube, as described in Japanese Patent Application Laid-open No. 2003-232395 (patent document 1) and Japanese Patent Utility Model Application Laid-open No. 60-157496 (patent document 2).
In the front fork described in the patent document 1, the partition wall member is mounted on an upper portion of the hollow pipe, and the partition wall member is held in the upper portion of the hollow pipe by being pressed by a suspension spring installed in the vehicle body side tube.
In the front fork described in the patent document 2, the partition wall member (a valve case 11) provided in the upper portion of the hollow pipe (a seat pipe 4) comprises a main body portion provided with the compression side damping valve. A mounting portion connected to the main body portion, and a small-diameter protruding portion provided in the mounting portion is fitted and fixedly provided in the upper portion of the hollow pipe.
In accordance with the front fork described in the patent document 1, since the partition wall member is only mounted to the upper portion of the hollow pipe, the oil moving from the oil chamber in an outer side of the hollow pipe to the lower oil reservoir chamber in an inner side of the hollow pipe during a compression stroke leaks into the upper oil reservoir chamber through a contact surface between the partition wall member and the upper portion of the hollow pipe, and further through an annular gap between an outer periphery of the partition wall member and an inner periphery of the vehicle body side tube. Further, the partition wall member is shifted in a diametrical direction in the upper portion of the hollow pipe. The shape of the annular gap between the outer periphery of the partition wall member and the inner periphery of the vehicle body side tube fluctuates, so that a flow path coefficient is changed. Accordingly, a compression side damping force property is not stable.
In accordance with the front fork described in the patent document 2, since a small-diameter protruding portion in the mounting portion constituting the partition wall member is fitted to the inner periphery of the upper portion of the hollow pipe, it is possible to inhibit the partition wall member from being shifted in a diametrical direction, which is preferable. However, for this structure, a number of parts in the partition wall member, working man-hours and assembling man-hours are increased and cost is increased.